Uses for a sputtering apparatus and a chemical vapor deposition (CVD) apparatus have increased in many fields as a thin film producing means for many kinds of materials. Specifically, substrates are successively processed by connecting a sputtering chamber for substrates, a loading chamber for the substrates, a heating chamber for the substrates, and an etching chamber and a removal chamber for the substrates for the purposes of increasing and stabilizing film characteristics of sputtered films in a mass production apparatus.
Each chamber of such apparatus is partitioned by a gate valve and usually is maintained in a vacuum condition without being opened to the air except for the loading chamber and the removal chamber.
The substrates are transferred one by one by a transfer means provided within the apparatus when the substrates are processed using the above-mentioned in-line type apparatus.
In such a case, the substrates are not transferred independently, but are transferred by being mounted on carriers, so-called trays or pallets (hereunder, substrate trays or trays).
The trays are transferred within the apparatus, and particular processes take place on the trays, after the substrates are set on the trays by an operator or robot outside of the apparatus. After the processes are finished, the operator or robot removes the substrates from the trays. After that, new substrates are set on the trays to permit performing the processes repeatedly.
The substrate trays are used repeatedly as mentioned above.
If the substrate trays happen not to be transferred perfectly, the production of the substrates is delayed, and trouble occurs in the frequency of transferring during the repeated usage of the substrate trays. The main reason for these troubles is thought to be distortion of the trays which is caused by thermal hysteresis due to heating during the sputtering of the substrates. When films fixed to the trays come off during the sputtering, the films are mixed with the sputtered films as dust, causing faulty products. To avoid this trouble, it is necessary to wash the trays.
Conventionally, operators have checked numbers provided on the trays, supervised the number of times of use of the trays, and exchanged and washed the trays after a predetermined number of times of use. Conventional automatic tray transfer line assembling apparatus has been proposed to provide a space for exchanging the trays other than at the substrate release portion. However, the apparatus has not provided a device for supervising the trays automatically.
In case of vertical type transferring of the substrate trays, when the substrates are set automatically using a robot, the trays are usually set in the state of vertical standing. Accordingly, this kind of apparatus does not necessitate a mechanism for laying the trays vertically or horizontally.
However, when the substrates are installed vertically, the substrates sometimes fall from the apparatus erroneously. The reason for this is that the structure of the vertical type tray is such that the thin substrate, having a thickness in the order of several mm, is set to a wide groove having a slightly large width compared with that of the thickness of the substrate.
To avoid this drawback, a method is proposed in which an inclination of the tray is calculated by a sensor provided on a hand of the robot, and automatic installation of the substrate is carried out accurately, as disclosed in FIG. 5 of the Japanese Patent Laid-Open No. 62-230973 entitled "Disc moving and mounting method of sputtering apparatus," published on Oct. 9, 1987.
Since the prior art mentioned above does not disclose an automatic supervising method relating to the repeated use and the amount of distortion of the tray, there remains a problem that difficulty in transferring the tray may arise on account of a delay in exchanging the tray, or a large stress or strain of the tray may occur, even when the tray is exchanged within a predetermined number of times of use.
When the trouble occurs with the apparatus, the processing chambers have to be opened to the air to permit overcoming the trouble. This considerably lowers the operation rate because of the start up time for the apparatus, and causes unstable film characteristics.
Since the above-mentioned Japanese Patent Laid-Open No. 62-230973 does not concern the strain of the whole trays, trouble occurs in the installation of the substrates when the trays are deformed.